Seepark Betzenhausen is Freiburg's easy urban green escape, built around a lake west of the historic centre. After the lanes, towers, and busy squares of the Altstadt, the park gives you open water, lawns, and room to slow down.
It is more local than monumental, but that is part of its usefulness. Go for a picnic, a walk, or a low-key afternoon with families and students, especially if you have already covered the cathedral and hillside viewpoints.